The present invention is directed to systems and methods for computing a relative path delay between multiple transmission sources, and more particularly to selecting a source which is closest to the receiving device based on a relative path delay estimation in orthogonal frequency division multiplexing (OFDM) systems.
Typically, a receiver (i.e., a mobile station (MS)) in a multiple transmission source (i.e., multiple base stations (BS)) system receives the same data signal from each transmission source and has to select one of the transmission sources to be the serving transmission source (i.e., the source from which the data is extracted and utilized). The receiver measures the power of each received signal (e.g., using a measure of Received Signal Strength Indicator (RSSI)) and selects the transmission source of the signal having the largest amount of power to be the serving transmission source.
However, because power of a signal received at a device does not correlate well with the distance to the transmission source from which the signal originated, these systems lack the capability to select the transmission source that is closest to the receiver. Additionally, although the transmission sources are synchronized to transmit the signals at the same time, the time at which the signals are received depends on the path delay between the receiver and the transmission sources. Thus, because these systems do not take into account distance when selecting a particular serving transmission source, the closest transmission source is not always selected which negatively impacts performance.
Accordingly, it is desirable to provide enhanced systems and methods for selecting a closest serving transmission source among multiple transmission sources to improve performance.